This study examined the internal structure and evidence of validity of the Test of Gross Motor Development 3 edition (TGMD-3) in primary school aged children. Participants (n = 1608, 47% girls, age range 5–11 years, mean age 9.2 ± 2.04) were recruited from Irish schools across twelve counties (56% rural, 44% urban). The TGMD-3 was used to measure FMS proficiency (Ulrich, 2020). A two-factor model (13 skills) was used and confirmatory indexes were calculated. The Bayesian criteria and the Composite Reliability were employed to evaluate alternative models. Relationships between the final model proposed with age, sex and BMI were calculated using a network analysis. Mplus 8.0 and Rstudio were used. A two-factor model (locomotion and object control) with adequate values (> 0.30) for the seven skills (gallop, hop, jump, two-hand strike, bounce, catch, overhand throw) presented excellent indexes. The skills with the highest indicator of strength centrality in the network were bounce and catch for both boys and girls and hop for boys and horizontal jump for girls. This study evidences the validity and reliability of the internal structure of the TGMD-3 and demonstrates that a short version of the TGMD-3, comprising seven skills is a valid measure of FMS in this population.